This invention relates to synthetic phosphoglyceride compounds, to methods of preparing such compounds, and to the use of such compounds in mediating platelet activation.
Applicants' have discussed background information relative to their invention in papers entitled "Platelet Activating Factor," 254 Journal of Biological Chemistry 9355-9358 (1979) and "Physicochemical and Functional Identity of Rabbit Platelet-Activating Factor (PAF) Released In Vivo During IgE Anaphylaxis with PAF Released in Vitro from IgE Sensitized Basophils," 123 Journal of Immunology 1847-1857 (1979). In applicants' papers the elucidation of functional and physicochemical properties of PAF were explored.
The platelet, now recognized as an important cellular element involved in the acute inflammatory process, has been strongly implicated in a variety of immunologically mediated forms of tissue injury including immune complex deposition and IgE induced systemic anaphylactic shock. Platelet participation in these disease processes likely involves a cooperative cellular interaction where antigen stimulated IgE-sensitized basophils and presumably mast cells release a chemical mediator, platelet activating factor (PAF) which in turn interacts with the platelets inducing aggregation and secretion of granular constituents. As a further consequence of platelet activation there may result a fatal reaction consisting of acute pulmonary hypertension, right heart dilation, systemic hypertension, significant increases in pulmonary vascular resistance, decreases in dynamic lung compliance and often complete pulmonary apnea.
The existence of a platelet activating factor was proposed in an article by Henson, P. M., 131 Journal of Experimental Medicine 287 (1970). Since that time the definition of its chemical structure and biochemical activity was not achieved due to the limited quanitities of material available for study.
One of the early reports on the chemical nature of PAF was that of Benveniste, J., 249 Nature 581 (1974). In this communication, Benveniste reported physico-chemical characteristics of PAF to include a molecular weight of approximately 1100 daltons, a PI near 10 and an ability to bind to bovine serum albumin. A later study by Benveniste, J., et al, 269 Nature 170 (1977) reported the purification of PAF isolates by successive thin layer chromatography with chloroform: methanol: acetic acid: water as the solvent system. On the basis of a spray reaction, they concluded that PAF was a phospholipid.
Other studies exploring the physico-chemical characteristics of PAF suggested that PAF was a relatively small molecule having a molecular weight ranging from 300-500 daltons. Additionally, data suggested it was stable to freezing, stable to heating at 56.degree. C. for 30 minutes, and stable at pH 3-10. No significant destruction by periodate, 2-mercaptoethanol and trypsin was noted, indicating PAF's resistance to oxidation, reduction and enzymatic attack respectively.
As more researchers released their findings certain inconsistencies became evident. For example the proposed molecular weight of PAF ranged from 300 to 1100 daltons. Moreover, one research group reported that PAF was inactivated by phospholipase D while another group reported suppression of PAF by phospholipase A and C but not by phospholipase D.